One early review dubbed it The Glums, but the people behind stage musical Les Miserables have a lot to smile about as it celebrates its 25th anniversary.

Les Miserables has been a global phenomenon - produced in 42 countries.

Based on Victor Hugo's door-stopper of a novel, it follows one man's story of survival in the face of persecution amidst social and political upheavals in 19th Century Paris.

The original London show, a collaboration between the Royal Shakepeare Company and Cameron Mackintosh, opened at the Barbican on 8 October 1985.

Despite mixed reviews - and a bum-numbing three-and-a-half hour running time - the musical found favour with audiences.

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The people are still singing: Les Mis is celebrating 25 years

It transferred to the Palace Theatre in December that year where it stayed until 2004. It then moved to the Queen's Theatre, where it still runs today.

To mark its 25th birthday, a special anniversary concert is being held at London's O2 Arena on Sunday. The one-off production will see members of the original 1985 cast perform alongside stars like teen idol Nick Jonas (of the Jonas Brothers) and Little Britain's Matt Lucas.

And as if that's not enough, a touring production has taken up a 22-date residency back where it all started - at the Barbican.

To mark the Silver Jubilee, here are 25 facts about the world's longest-running musical:

I DREAMED A DREAM

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Alfie Boe as prisoner 24601, Jean Valjean

1. The original French version of the show - by lyricist Alain Boublil and composer Claude-Michel Schonberg - ran for 107 performances in 1980 at the Palais des Sports in Paris.

2. The London production was co-directed by John Caird and Trevor Nunn. The English lyrics were by Herbert Kretzmer - who at the time was TV critic for the Daily Mail.

3. That didn't stop the Mail on Sunday's Kenneth Hurren writing in his 1985 review: "Watching it is rather like eating an artichoke: you have to go through an awful lot to get a very little."

4. Michael Ball, who played Marius, has told the BBC since: "We thought we'd be looking for new jobs after the first night."

5. In the original London production, the role of Inspector Javert was played by Roger Allam - who can currently be seen in the film Tamara Drewe.

6. The role of thieving innkeeper Thenardier was played by Alun Armstrong, who currently stars in the BBC series New Tricks.

DO YOU HEAR THE PEOPLE SING?

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Nick Jonas plays hero Marius Pontmercy

7. There are approximately 101 cast and crew directly involved in every performance.

8. Each performance requires 392 complete costumes - and 31 wigs.

9. There have been almost 40 cast recordings of Les Miserables.

10. On 22 January 2010, the show celebrated its 10,000th performance in London.

11. The RSC is estimated to have made £19m from royalties from touring productions.

12. Productions have played in 42 countries including Iceland, New Zealand, Bermuda, Philippines, Mauritius, China, Mxico, the Channel Islands and the Dominican Republic.

AT THE END OF THE DAY

15. Contrary to popular opinion, the musical is NOT set during the French Revolution of 1789. The action begins in 1815, and follows events over the next two decades including the Paris Uprising of 1832.

16. Les Miserables is the third longest running show in Broadway history after Phantom of the Opera and Cats.

17. The Les Miserables schools edition was launched in the US in 2001 and in the UK in 2002.

18. In school productions, the entire cast must be 19 years of age or under, and must be amateurs.

19. The biggest single live audience for Les Miserables to date was 125,000 at the 1989 Australia day concert in Sydney.

20. In 2004, a special concert performance was given at Windsor Castle in honour of French President Jacques Chirac to celebrate the centenary of the entente cordiale - Britain's friendly agreement with France.

ONE DAY MORE

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Matt Lucas will play Thenardier in the 02 anniversary production

21. Les Miserables celebrated its 10th anniversary with a gala concert at the Royal Albert Hall, London.

22. The concert starred the original Jean Valjean, Colm Wilkinson. The finale featured 17 different Jean Valjeans from around the world singing in different languages.

23. Les Miserables became the West End's longest-running musical on 7 October 2006. On that night super-fan Sally Frith from Gloucestershire saw the show for the 740th time.

24. In 2009, Susan Boyle sang Les Mis song I Dreamed a Dream on TV show Britain's Got Talent. It became one of the most watched videos on YouTube.

25. Producer Sir Cameron Mackintosh is currently developing a film version of the musical. (The first movie version of the novel Les Misérables was a silent film in 1909. There were no songs.)